Climate change

Recap from Feb 4th: Trade-offs

Resource acquisition trade-offs

  • once resource instead of another

    • seed size vs. dispersal

    • getting a degree vs getting a job

    • CAM plants (open stomata at night): only CO2 at night but hang onto its water = slow growth rate overall VS. C3 plants grow quickly but need more water to work

Resources allocation trade-offs

  • one purpose instead of another

    • fish growing (to reproduce later) instead of reproducing early

Feb 6th: Climate change

1) CO2 and other gases create a greenhouse effect that captures heat

  • Greenhouse effect: energy comes in from the sun, hits the earth’s surface, re-radiates back into space, and some proportion is absorbed by the atmosphere and radiates back onto the earth

  • Ice age: periods that were colder

Earth’s energy budget:

  • ALl energy comes from the sun: solar radiation

    • some are immediately reflected back into atmposhere

    • majority (70%) is absorbed by land, ocean, within the atmosphere(clouds) ===> heats up the earth’s surface

    • the absorbed energy is re-radiated back out

> Changes in the type of surfaces: energy absorbed by water vs. energy absorbed by land

  • feedback loops: glaciers melting that can have a big impact

Milankovitch cycles: natural changes in sun’s intensity that affect the earth’s climate; earth’s orbit responsible for ice ages; LONG time spans

  • earth tilt(T)

  • shape of orbit around the sun (E)

  • earth’s wobble on its orbit (P)

QUICK natural changes:

  • volcanic activity affecting the reflectivity of the earth’s atmosphere

    • the ash and other chemicals increase the radiation reflected bc the land and water can’t absorb it (they block it from coming to the land)

    • changes the amount of radiation that is immediately reflected back into space

    • can lead to: crop failures, livestock death

QUICK human-caused changes

a) changing the amount of energy reflected (earth surfaces)

b) changing the amount absorbed by the earth’s atmosphere

  • increasing the amount of greenhouse gases (more is absorbed by the earth’s atmosphere)

    • CO2

    • N2O

    • CH4

    • fluorinated compounds

    • water vapor

  • Global warming potential = warming effect and residence time (set relative to COs); how effective a gas is at absorbing the radiation and how long it sticks around in the atmosphere

> water vapor is low bc of low residence time and absorbance of radiation

Relative order

Climate impact = GWP * quantity of the gas

anthropogenic: man-made

  • CO2 is the highest man-made

H2O is the naturally occurring (not directly emitted)

Negative feedback: a system in which a change promotes other changes that bring it back to the original state

  • toward equilibrium

  • shivering/sweating

Positive feedback: A change promotes further change toward an extreme

  • labor and contractions

Water Vapor Feedback: positive feedback

1) CO2 ++

2) global temp ++

3) increases evaporation = increased water vapor === more ++ in temp

Other + feebacks:

> Warm air holds more water vapor

  • cold air can condense it into a liquid

> Warm water holds less dissolved CO2 = release more CO2 (+t)

> Decreasing reflectivity of earth’s surface

  • Albedo: the reflectivity of a surface

    • color of surfaces: dark surfaces absorb more light (infrared radiation: heat)

2) Human CO2 emissions alter the global climate and future projections

We can know how past climate changes occurred through:

  • gas bubbles trapped in ice cores: drill down into ice to get cores

    • snowflakes trapping air: sample of the atmosphere

  • chemistry of fish otoliths

    • count backward (bone was formed) and analyze the oxygen atoms in a ring and distinguish based on oxygen isotopes (some are more likely to form as rain vs snow)

  • growth rates in tree rings

    • count backward to see how much they grew

> Climate and Carbon are highly correlate

> Current CO2 is higher and increasing more rapidly than in the past

  • fossil fuel consumption increased exponentially in the last years

Make predictions based on a model, then put in an estimate (projections in a range)

Emission scenarios: different choices humans can make

  • business as usual

  • immediate reductions

The International Panel on Climate Change (IPCC) made their first report in 1990

> Predictions on sea level rise based on different emission scenarios

  • happens gradually cause it takes time for ice to melt

Short-term: Projections on temperature

Recent past: drought data; total % of area in the US